In that by a rough count, you said that you are nice to her, but she is mean to you, about four times in two paragraphs in your response, I think you are evading the issue.
I did not question your fatherhood, but your motivation to give your son a gift knowing that it would at least passively annoy and upset your ex-wife.
This goes to my original point, that Christmas gifts are about emotional content. Any other time of the year you could have given your son a gun, no problem, even if it did irritate your ex-wife.
But doing it on Christmas will imply to your son, actively or passively, that your negative feelings towards your ex-wife are more important than your positive feelings to him. He is likely very aware that his mother abhors guns, so what would you expect him to think?
I didn’t mean to imply that you were questioning my fathering skills. That was another poster, who I said “up yours” to at the end of my comment to you. I forgot to ping her, so I pinged her in my next comment.